Git Webhooks

Argo CD supports Git webhooks, which can be used to trigger automated deployments whenever changes are pushed to your Git repository. In this way, Argo CD can react immediately to changes, ensuring that your cluster's state always matches the desired state defined in your Git repository. To use Git webhooks with Argo CD, you need to configure a webhook in your Git repository to send requests to the Argo CD API server whenever changes are pushed to the repository.

The exact steps to configure a webhook depend on your Git provider, but generally, you'll need to provide the URL of the Argo CD API server and a secret that Argo CD can use to validate the webhook requests. For example, to configure a webhook in GitHub:

• Go to the Settings page of your GitHub repository.
• Click Webhooks , then Add webhook .
• In the Payload URL field, enter the URL of your Argo CD API server with the path /api/webhook (e.g., if your Argo CD API server is at https://argocd.example.com , you would enter https://argocd.example.com/api/webhook ).
• In the Content type field, select application/json .
• In the Secret field, enter a secret of your choice. You'll need to provide this secret to Argo CD so it can validate the webhook requests.
• Select Just the push event to trigger the webhook only when changes are pushed to the repository.
• Click Add webhook to save the webhook.

Once the webhook is configured, GitHub sends a POST request to the Argo CD API server whenever changes are pushed to your repository. To configure Argo CD to use the webhook, you need to create a webhook secret in the same namespace as the Argo CD API server. This secret should contain the same secret you used when configuring the webhook in your Git repository. For example:

kubectl create secret generic github-webhook-secret --from-literal=secret=<your-webhook-secret> -n argocd

Replace <your-webhook-secret> with the secret you used when configuring the webhook in your Git repository.

With the Git webhook and the Argo CD webhook secret configured, Argo CD automatically syncs your applications whenever changes are pushed to your Git repository, ensuring that your cluster's state always matches the desired state defined in your Git repository and providing a truly automated GitOps experience.

Resource Health

Argo CD provides a comprehensive system for monitoring and reporting the health status of application resources. This system allows you to identify issues quickly and take corrective action, ensuring that your applications remain healthy and functional. Argo CD uses health checks to determine the status of application resources. These health checks are based on the resource's status field, which is part of the standard Kubernetes resource specification.

By default, Argo CD includes built-in health checks for many common Kubernetes resource types, such as Deployments, StatefulSets, DaemonSets, and more. For these resource types, Argo CD can automatically determine the health status on the basis of the resource's status field.

For example, for a Deployment resource type, Argo CD considers the deployment healthy if the number of up-to-date replicas matches the number of desired replicas. In addition to the built-in health checks, Argo CD allows you to define custom health checks for other resource types. You can define a custom health check by creating a Lua script that checks the resource's status field and returns a health status. You can find an example of a custom health check for a hypothetical MyResource resource type in Listing 10.

hs = {}
if obj.status.phase == "Running" then
  hs.status = "Healthy"
elseif obj.status.phase == "Pending" then
  hs.status = "Progressing"
  hs.message = "Resource is in the Pending phase"
else
  hs.status = "Degraded"
  hs.message = "Resource is in an unknown phase"
end
return hs

The health check considers the MyResource resource healthy if its phase is "Running", progressing if its phase is "Pending", and degraded otherwise.

You can view the health status of your application resources in the Argo CD UI, which displays a health status icon for each resource, allowing you to identify any issues quickly. Additionally, you can use the argocd app get command to view the health status of an application:

argocd app get my-app

This command displays information about the my-app application, including the health status of its resources.

Monitoring Argo CD

The Argo CD monitoring features allow you to track the state of your applications in real time. The dashboard provides a visual overview of your applications, including their sync and health status. You can drill down into each application to see detailed information about the individual resources.

In addition to the dashboard, Argo CD exposes Prometheus metrics that you can use to monitor the state of your applications and the performance of Argo CD itself. These metrics can be scraped by a Prometheus server and visualized by a tool like Grafana.

To configure a Prometheus server to scrape metrics from Argo CD, use

scrape_configs:
  - job_name: 'argocd'
    static_configs:
      - targets: ['argocd-metrics-service:8082']

In this example, the Prometheus server is configured to scrape metrics from the argocd-metrics-service on port 8082.

Argo CD supports notifications that alert you to changes in the state of your applications. Notifications in Argo CD are handled by the Argo CD Notifications plugin, which supports a variety of notification methods, including email, Slack, and more.

To set up notifications, you need to create a ConfigMap and a Secret that define your notification settings and credentials (Listing 11). The ConfigMap defines a Slack service with a webhook URL, and the Secret provides the Slack token.

apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-notifications-cm
data:
  service.slack: |
    - url: https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX
---
apiVersion: v1
kind: Secret
metadata:
  name: argocd-notifications-secret
stringData:
  slack-token: 'your-slack-token'